Aircrafts are generally provided with cockpit windshield assemblies of which the window panes or transparent members are flat, which gives the windshield assembly a convex shape with multiple flat facets which are joined with the front part of the fuselage. This technical solution enables transparent members of limited cost to be used for the window panes and simple window pane frames. However, this type of windshield assembly locally gives rise to a high aerodynamic drag.
To reduce the aerodynamic drag of the aircraft in the region of the windshield assembly, it is known to use window panes for that assembly which have dual curvature. This horizontally and laterally curved shape of the window panes joins perfectly with the shape of the fuselage and enables significant reductions in aerodynamic drag.
Numerous aircraft windshield assemblies possess six window panes (two in a front position, two in a side position and two in a rear position, relative to the pilots) of which the two front window panes are mounted and fastened with flanges from outside the aircraft. This is because the presence of the navigation screens of the cockpit does not enable mounting of the front window panes from inside the aircraft.
This embodiment for mounting the front window panes enables fast replacement of the window panes, without constraint on the utilization of the machine. The recourse to mechanical ways of mounting the window panes with sealant-free joints makes it possible to avoid the use of sealing mastics of which the curing may exceed 24 hours and which lead to relatively complex demounting and cleaning of the structures.
For the other four window panes, (lateral and rear), when not prevented by any item of equipment inside the cockpit, the mounting is preferably carried out from inside the cockpit since the pressure which is ambient inside the cabin in cruising conditions promotes the sealing and the safety of this part of the windshield assembly. This solution for mounting the window panes from inside the cockpit is also advantageous for minimizing the mass of the elements for joining the window panes with the structure of the windshield assembly.
However, the mounting of literal and rear window panes with dual curvature from inside the cockpit generates a large cavity between the structure and the transparent member.
In case of bird strikes on the windshield assembly of the cockpit, the birds are transformed into liquid and gas which the cavity or cavities become charged with. The deformations of the window panes and of the framing structure which result therefrom may have a damaging effect on the windshield assembly.
Numerous civil and military aircraft, of small size, which generally have no cabin pressurization, have windshield assemblies with a dual curvature, but the technical solutions for connecting the transparent members with the structure do not have cavities liable to weaken those zones when bird strikes occur.